K3: Audio Balance in AFX Modes

[Joel R. Hallas]

I just installed some new speakers, one on each side, to be ready for
two-frequency reception whenever I get the second receiver.

 

I noticed a lack of balance between the two channels while using  AFX. At
first I thought it was a speaker problem, but after swapping  everything
from side to side without change, I noticed that it was nicely balanced if I
turned AFX off.

 

I realize that with the second receiver it won't be a problem, since there
are separate AF gain controls for each channel - still it would be nice to
have the AFX working as it should. Does anyone know of a way to adjust the
balance between the two AFX channels, other than padding one of the
speakers?

 

Regards, Joel

Joel R. Hallas, W1ZR

K3 - 431

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[KK7P]

Hello Joel!

> I noticed a lack of balance between the two channels while using  AFX. At
> first I thought it was a speaker problem, but after swapping  everything
> from side to side without change, I noticed that it was nicely balanced if I
> turned AFX off.

Is this with voice or CW?

Since AFX introduces delay, there will be nulls and peaks in audio
response as the audio signals add or subtract from each other based on
the pitch - hence relative phase - of the signal(s).

73,

Lyle KK7P

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[Joel R. Hallas]

Lyle,

Well I took a few minutes of data, as you suggested, using an XG-1 CW
generator, and found the level the same on both sides, whether the AFX was
on or off. I put it back on the antenna -- the speakers are now mounted on
the wall, a short distance away and didn't notice a problem either.

So for now, I'll chalk it up to some kind of "perceptual dysfunction."  

Regards, Joel
Joel R. Hallas, W1ZR
-----Original Message-----
From: Lyle Johnson [mailto:[hidden email]]
Sent: Friday, August 15, 2008 4:10 PM
To: Joel R. Hallas
Cc: wayne burdick; Lyle Johnson
Subject: Re: [Elecraft] K3: Audio Balance in AFX Modes

Hello Joel!

> This is the case with either mode, and stays the same over time, so I
> suspect not a phase shift issue. It also doesn't switch back and forth as
it
> would if it were based on phase.

I looked over the DSP code and saw nothing that might result in this
symptom.

I then connected my K3 to my dual channel 'scope and checked DELAY1,
2..5, as well as BIN on LINE OUT, then PHONES (rear jack) then EXT SPKR.
  I tried AFX ON and OFF.  I tried USB as well as CW modes.

In all cases, the signal level is consistent between the two channels
and essentially the same levels.

I assume you have SPKR 2 selected in the CONFIG:SPKR menu.

How much amplitude difference are you seeing betwewn the two channels?
Which channel is weaker?  WHat is the nominal impedance of the speakers
you are connecting?

73,

Lyle KK7P

> Regards, Joel
> Joel R. Hallas, W1ZR
> -----Original Message-----
> From: Lyle Johnson [mailto:[hidden email]]
> Sent: Friday, August 15, 2008 2:55 PM
> To: Joel R. Hallas
> Cc: [hidden email]
> Subject: Re: [Elecraft] K3: Audio Balance in AFX Modes
>
> Hello Joel!
>
>> I noticed a lack of balance between the two channels while using  AFX. At
>> first I thought it was a speaker problem, but after swapping  everything
>> from side to side without change, I noticed that it was nicely balanced

if

> I
>> turned AFX off.
>
> Is this with voice or CW?
>
> Since AFX introduces delay, there will be nulls and peaks in audio
> response as the audio signals add or subtract from each other based on
> the pitch - hence relative phase - of the signal(s).
>
> 73,
>
> Lyle KK7P
>
>
>

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[Bill W4ZV]

Joel R. Hallas wrote

I just installed some new speakers, one on each side, to be ready for
two-frequency reception whenever I get the second receiver.

Just my opinion, but if you plan to use diversity (i.e. same frequency, not split) with the KRX3, you'll have much better results with stereo headphones.  Unless you place your head exactly between your speakers, you'll be introducing phase shift...not to mention reflections from your room...which may distort the diversity effect.

73,  Bill